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faSSflsTIVERSITY  OF  CINCINNATI 

THE  USRAHt 
Bulletin  No.  XII  gf  jg£ 

WWMUTlfOFIU.tSlOlS 

APRIL  1902. 


Publications  of  the  University  of  Cincinnati 
Skriks  II.  Voi,.  II. 


A  Syllabus  of  Lectures 


DARWINISM  and  EVOLUTION 

by 

DR.  M.  R  GUYER. 


The  University  Bulletins  are  Issued  Quarterly 


Entered  at  the  Post  Office  at  Cincinnati,  Ohio,  as  second-class  matter 


UNIVERSITY  PRESS 
Cincinnati,  Ohio 


UNIVERSITY  OF  CINCINNATI 

'Department  of 'Biology. 

CINCINNATI  TEACHERS'  UNIVERSITY  CLUB 
OF  NATURAL  HISTORY. 


Syllabus  of  a  Course  of  Illustrated  Lectures 

...ON... 

DARWINISM  and  EVOLUTION 

By 
DR.  MICHAEL  F.  GUYER. 


These  lectures  are  open  to  the  public  and  a  cordial  invitation 
is  extended  to  all  persons  interested. 


SIX  LECTURES— FRIDAY  EVENINGS 

at  8:00  P.  M.  in  CUNNINGHAN  HALL. 

April  18th,  and  25th.  May  2d,  9th,  16th  and  23rd. 


UNIVERSITY  PRESS 

Cincinnati,  Ohio 

J902. 


COLLATERAL  READING. 


It  is  recommended  that  the  student  read  one  or  more  of 
the  following  books  on  Darwinism  and  Evolution: 
Wallace:  Darwinism. 
Darwin:  Origin  of  Species. 
Darwin:  The  Descent  of  Man. 

Huxley:  Encyclopedia  Britannica, 
"Evolution  in  Biology." 

Huxley:  Collected  Essays,   "Darwiniana." 

Haeckel:  History  of  Creation. 

Jordan:  Foot-notes  to  Evolution. 

Romanes:  Darwin  and  after  a  Darwin,  Vol.  I. 


,       x-  ,  LECTUEE  I. 

AN  EVENING  WITH  THE  MICROSCOPE. 

A  demonstration  of  microscopic  forms.  The  living  organisms 
will  be  projected  through  the  microscope  onto  a  screen.  Opera 
glasses  will  be  found  useful. 

"To  gaze  into  that  wonderful  world  which  lies  in  a  drop  of 
water,  crossed  by  some  atoms  of  green  weed ;  to  see  transparent  liv- 
ing mechanism  at  work,  and  to  gain  some  idea  of  its  modes  of  ac- 
tion; to  watch  a  tiny  speck  that  can  sail  through  the  prick  of  a 
needle's  point;  to  see  its  crystal  armor  flashing  with  ever-varying 
tints,  its  head  glorious  with  the  halo  of  its  quivering  cilia;  to  see 
it  gliding  through  the  emerald  stems,  hunting  for  its  food,  snatch- 
ing at  its  prey,  fleeing  from  its  enemy,  chasing  its  mate  (the  fiercest 
of  our  passions  blazing  in  an  invisible  speck) ;  to  see  it  whirling  in 
a  mad  dance  to  the  sound  of  its  own  music — the  music  of  its  happi- 
ness, the  exquisite  happiness  of  living— can  any  one  who  has  once 
enjoyed  this  sight,  ever  turn  from  it  to  mere  books  and  drawings 
without  the  sense  that  he  has  left  all  fairyland  behind  him?" — 
Hudson. 

LECTUEE  II. 

DARWINISn  AND  EVOLUTION;  HISTORICAL. 

1.  Statement  of  the  Problem.— The  wealth,  diversity  and 
adaptations  of  animals  and  of  plants ;  how  produced.  Naturalists 
classify  living  organisms  according  to  their  resemblances  into 
groups  termed  species,  but  this  is  only  a  convenience  and  is  not 
warranted  by  any  sharp  line  of  demarcation  in  nature.  The  old 
idea  of  species  due  to  ignorance;  variations  regarded  as  nuisances. 
Despite  the  enormous  number  of  species,  a  unity  of  type  is  appar- 
ent ;  all  forms  of  animals  or  of  plants  can  be  reduced  to  a  few  gen- 
eral plans  of  structure,  or,  broadly  considered,  to  one.  Is  similar- 
ity in  structure  due  to  identity  of  parentage? 

2.  Some  answers  to  the  Problem.— The  theory  of  special  cre- 
ation; species  were  created  in  the  beginning  as  they  exist  today. 
Special  creation  the  belief  of  Linnaeus;  he  knew  three  thousand  spe- 
cies, but  modern  naturalists  know  hundreds  for  his  every  one.  Cu- 
vier  and  the  immutability  of  species.  Necessity  of  explaining  fos- 
sil forms,  the  foundation  for  his  doctrine  of  successive  creations  and 
destructions  of  organisms  (doctrine  of  Catastrophism).     Evolution 

(3) 


a  theory  of  the  blood  relationship  of  living  organisms.  It  states 
that  the  wide  variety  of  existing  organisms  is  due  to  the  divergence 
of  offspring  from  a  common  ancestry  to  form  dissimilar  groups 
through  the  accumulation  of  variations  in  successive  generations. 
The  idea  of  evolution  is  an  old  one ;  no  one  man  can  be  cited  as  its 
author.  In  the  theories  of  the  Greeks,  Lucretius,  Buffon,  Erasmus 
Darwin,  Lamarck  or  St.  Hilaire,  an  adequate  explanation  of  how 
evolution  came  about  was  lacking.  Charles  Darwin  and  Alfred 
Eussell  Wallace.  Darwinism  is  not  synonomous  with  evolution,  but 
one  explanation  of  how  evolution  has  been  effected.  A  natural  law 
is  simply  what  common  sense  has  shown  to  be  the  sequence  of  events. 
Darwin's  explanation  of  evolution  is  founded  on  universally  admit- 
ted facts  (natural  laws),  which,  were  there  no  further  evidence, 
lead  to  the  conception  of  evolution  as  a  logical  necessity.  On  the 
other  hand,  were  the  Darwinian  theory  swept  away  the  evidences  of 
evolution  are  in  no  wise  shaken. 

3.  The  Starting  Point  of  the  Darwinian  Theory. — 

a.  The  new  theory  of  the  earth  (Hutt on— "Theory  of  the 
Earth/'  Lyell— "Principles  of  Geology").  Natural  agencies  now 
at  work  were  shown  to  be  not  only  competent  to  produce  the  pres- 
ent geological  conditions  of  the  earth,  but  inevitably  to  have  done 
so. 

b.  Similarity  in  structure  and  habits  between  the  species  of 
plants  and  animals  of  islands  and  the  species  of  the  neighboring 
mainland  led  Darwin  to  the  conclusion  that  the  islands  had  been 
colonized  from  the  mainland  and  that  the  insular  forms  had  di- 
verged sufficiently  from  the  original  stock  to  constitute  different 
species.  Kindred  peculiarities  of  structure  between  certain  fossil 
and  recent  animals  of  South  America  found  their  obvious  explana- 
tion in  the  view  that  the  recent  forms  were  the  modified  descend- 
ants of  the  extinct  forms. 

c .  The  power  possessed  by  man  of  producing  deviations  from 
wild  types  under  domestication  (artifical  selection).  Man  pro- 
duces new  breeds  of  animals  or  new  varieties  of  plant  at  will,  in- 
ducing modifications  more  marked  than  those  which  separate  wild 
species.  Though  there  is  a  tendency  of  offspring  to  resemble  pa- 
rents, no  two  individuals  are  exactly  alike  (heredity  and  variation). 
Variations  occur  in  every  direction.  Man  selects  such  modifications 
as  meet  his  needs  or  his  fancy  and  by  propagation  generation  after 
generation  slowly  builds  up  the  type  he  desires ;  for  example,  apples, 
roses,  cabbages,  poultry,  pigeons  and  dogs. 

Variations  usually  slight;  more  rarely,  marked  variations 
termed  saltatory  variations  or  "sports"  appear.  The  breed  of  Ancon 
sheep  is  the  result  of  a  saltatory  variation.  Two-legged  dogs  of  Cin- 
cinnati.      The  question  confronted  Darwin,  if  variations  are  so 

(4) 


universal,  is  there  anything  in  nature  which  operates  so  as  to  favor 
certain  variations  and  to  suppress  others,  thus  modifying  the  form 
or  habits  of  the  organism? 

d.  Malthus  on  population.  Malthus  pointed  Out  that,  unless 
checked  by  famine,  disease,  war  or  the  like,  the  tendency  of  popula- 
tion is  to  increase  more  rapidly  than  do  means  of  substance.  The 
doctrine  of  Malthus  provided  Darwin  with  a  theory  by 
which  to  work.  It  is  a  remarkable  coincidence  that  this  essay  led 
both  Darwin  and  Wallace  independently  to  inquire  if  there  were  not 
similar  checks  in  the  case  of  animals  and  plants,  and  if  so  as  to 
which  individuals  Would  survive. 

LECTUEE  III, 
THE  DARWINIAN  THEORY. 

1 .  Living  Organisms  enormously  fertile  yet  the  total  number 
approximately  stationary -If  the  tendency  of  any  one  species  to 
increase  were  unchecked,  in  a  very  short  time  no  country  could  sup- 
port the  product  nor  the  world  hold  it.  The  female  grasshopper  lays 
on  average  100  eggs;  if  these  mature  (50  males  and  50  females) 
and  multiplication  goes  on  unchecked,  at  the  end  of  seventeen  years 
the  number  would  be  absolutely  inconceivable*  expressed  in  weight 
it  would  amount  to  fifteen  times  the  weight  of  the  earth.  The  roe  of 
a  codfish  contains  10,000,000  eggs.  If  the  number  of  the  species  is 
to  remain  constant,  it  means  that  of  the  descendants  but  two  indi- 
viduals mature  to  take  the  place  of  the  parents,  for  example,  only 
two  of  the  10,000,000  eggs  of  the  codfish  attain  maturity. 

2.  The  Struggle  for  Existence.— A  vast  majority  of  the  or- 
ganisms which  come  into  the  world  are  doomed  to  early  death,  hence 
there  is  fierce  competition  for  existence.  The  struggle  may  be 
either  sanguinary  or  passive,  it  is  inevitable  in  any  event,  Checks 
to  increase  in  plants;  in  grasshoppers.  The  microscopic  organisms 
of  the  ocean  are  the  ultimate  food  supply  of  all  marine  animals.  The 
cycle  of  life.      The  threefold  nature  of  the  struggle : 

a.  Rivals. — Competition  is  often  severest  between  individuals 
of  the  same  species  or  with  closely  allied  forms  (for  food,  position, 
mates*  etc.). 

h.    Hazards  of  the  Chase. — "    *     *     * 

How  lizard  fed  on  ant,  and  snake  on  him; 
And  kite  on  both ;  and  how  the  fishhawk  robbed 
The  fish4iger  of  that  which  it  had  siezed; 
The  shrike  chasing  the  bulbul,  which  did  chase 
The  jewelled  butterflies;  till  everywhere 
Each  slew  a  slayer  and  in  turn  was  slain, 


c.  Struggle  with  Inanimate  Nature.— The  past  winter  has 
done  more  to  exterminate  the  quail  in  Ohio  than  would  a  small 
army  of  sportsmen  in  the  same  time.  In  human  society  600,000 
are  estimated  to  have  died  in  two  years  as  the  result  of-  a  potato 
famine  in  Ireland. 

3.  Variation  and  Heredity.— Variation  and  heredity  together 
with  the  struggle  for  existence  render  evolution  possible.  That 
variation  is  widespread  in  nature  is  shown  by  the  difficulties  of  sys- 
tematists  in  classifying  plants  and  animals  into  species.  Examples: 
willows,  brambles,  fishes,  snails.  Percentage  of  variation  from  meas- 
urements of  various  animals.  Examples  of  variation  in  man.  Varia- 
tions may  affect  any  part  and  in  any  direction.  Variation  in  habits 
illustrated  by  the  Kea  of  New  Zealand.  The  origin  of  variations  is 
the  fundamental  question  in  evolution,  but  one  which  has  never 
been  satisfactorily  answered.  The  following  factors  have  been  sug- 
gested : 

a.  Dual  ancestry.  Offspring  derived  from  two  ancestors,  a 
blend  or  compromise  between  the  parents. 

b.  An  inherent  tendency  to  vary.  The  instability  of  living 
matter. 

c.  Use  and  disuse  of  organs.    A  questionable  factor. 

d.  The  direct  action  of  environment.  An  unknown  quantity 
Changes  in  nutrition,  etc.,  in  many  plants  may  be  followed  by  va- 
riation. 

Darwin's  theory  not  an  endeavor  to  explain  variations,  but  to 
determine  the  factors  which  direct  variations. 

4*  Natural  Selection   (Darwin) ,   or  Survival  of  the   Fittest 

(Spencer). — Of  the  vast  number  of  individuals  which  must  battle 
for  a  place  in  the  world,  some  possess  advantageous  variations  in 
certain  directions  and  are  in  consequence  able  to  surpass  their  com- 
petitors. The  favorable  features  are  handed  down  to  descendants 
and  intensified  so  long  as  they  continue  to  be  advantageous.  Thus, 
organisms  become  more  and  more  perfectly  adapted  to  the  condi- 
tions of  life.  In  artificial  selection  man  chooses,  in  natural  se- 
lection the  process  is  brought  about  automatically  through  the 
struggle  for  existence;  the  weak,  the  inexpedient,  the  ill  adapted  are 
eliminated*  the  forms  most  in  harmony  with  their  surroundings  sur- 
vive. Natural  selection  well  illustrated  by  the  wingless  insects  of 
the  Kerguelen  islands  and  of  Madeira.  How  the  grasshopper  got  its 
color.     Adaptations  in  nature  concerned  mainly  with: 

a.  Procuring  food. 

b.  Perpetuation  of  the  race. 

c.  Self -protection.  .     ;; 

d.  Adjustment  to  physicial  surroundings. 

(6) 


The  world  of  guile;  protective  coloration  (general) ;  leaf  but- 
terflies, stick  caterpillars,  etc.;  aggressive  coloration;  warning  col- 
ors ;  mimicry  ;  lures.  Occupancy  of  a  given  region  an  important  ad- 
vantage to  a  species  and  survival  may  be  "Survival  of  the  Existing  v 
(Jordan),  and  not  necessarily  "Survival  of  the  Fittest."  Natural 
selection  regarded  by  Darwin  as  the  most  powerful  agent  in 
organic  evolution. 

5*  Changing  Environment  Necessitates  Continued  Structural 

Modifications  ♦-Perfect  adaptation  impossible;  living  organisms 
must  continually  adjust  themselves  to  the  shifting  conditions  of 
life. 

a.  Climatic  Changes. — The  former  warm  climate  of  Green- 
land. Much  of  North  America  modelled  by  moving  ice,  hence 
former  climatic  conditions  unlike  the  present. 

b.  Geographic  Changes: —  Alternate  lifting  and  depression  of 
the  earth's  crust.  Changes  in  the  vicinity  of  Cincinnati.  Isolation; 
the  fauna  of  islands.     The  removal  of  barriers. 

c.  Fluctuations  in  Food  Supply. — The  advantages  and  disad- 
vantages of  specialists;  the  giraffe  and  the  ant-eater. 

d.  Destructive  Checks. — A  saturation  point,  so  to  speak,  is 
reached  sooner  or  later  by  a  species  in  a  given  region;  loss  exactly 
balances  increase.  The  diminution  of  destructive  checks  may  allow 
disturbance  of  this  equilibrium  of  nature.  Spread  of  the  English 
sparrow  in  America.  Scale  insects.  Weeds. 

If  certain  members  of  a  species  meet  the  conditions  of  life 
by  variation  in  one  direction  and  others,  in  other  directions,  then 
the  continued  action  of  natural  selection  must  in  time  lead  to  suffi- 
cient divergence  betwen  the  forms  to  make  them  rank  as  separate 
species.  This  is  what  Darwin  means  by  "Origin  of  Species."  The 
same  process  continued  through  the  millions  of  years  which  have 
elapsed  since  the  first  life  appeared  on  the  globe  is  sufficient  to 
have  given  rise  to  the  entire  diversity  of  the  life  of  to-day. 

6.  Summary  of  the  Argument, — Wallace's  chart. 

FACTS.  CONSEQUENCES. 

a.     Rapid  increase  of  organisms. 


Struggle  for  Existence. 

b.  Total  number  stationary. 

c.  Struggle  for  existence.  )    Survival  of  the  Fittest 

l  or 

d.  Variations  with  heredity.        )    Natural  Selection. 


e.    Survival  of  the  fittest.  )    Structural  modifications  lead- 

/.     Changing  environment.  )    ing  to  Origin  of  Species. 

(7) 


LECTUKE  IV. 

EVOLUTION:  EVIDENCE  FROM  THE  PRESENT  STRUCTURE 
AND  DISTRIBUTION  OF  ANIMALS. 

U  The  Present  State  of  Opinion.— That  existing  plants  and 
animals  are  the  modified  descendants  of  more  primitive  forms  is 
now  universally  conceded.  The  greatest  uncertainty  is  as  to  how 
the  various  changes  have  come  about.  Origin  of  variation  is  the  pri- 
mary factor.  Darwinism  (natural  selection)  is  widely  accepted  as 
one  of  the  most  important  secondary  factors.  The  search  for  un- 
known  factors;  the  apparent  purposeful  character  of  certain  varia- 
tions. 

2.  The  Classification  of  Animals.— Classification  consists  in 
grouping  animals  according  to  similarity  in  fundamental  structure. 
A  species  is  the  smallest  group  to  which  constant  characters 
(not  sexual)  can  be  assigned;  genera  are  groups  of  species  pos- 
sessing features  in  common;  on  this  same  principle  of  inclusion 
families,,  orders,  classes  and  phyla  are  successively  constructed.  The 
entire  system  is  conventional  and  as  we  learn  more  about  animal 
forms  we  find  that  the  groups  merge  imperceptibly  into  one  an- 
other. The  only  plausible  explanation  of  the  facts  is  that  varieties 
diverge  slowly  to  form  species  which  in  turn  become  sufficiently  dif- 
ferent to  be  ranked  as  separate  genera  and  thus  gradually  the  whole 
kinship  of  life  has  been  established. 

3.  Similarity  in  the  Architecture  of  Animals Structural 

correspondence  of  organs  (homology)  is  the  most  striking  feature 
of  animal  forms.  The  skeleton  of  vertebrates  retains  its  funda- 
mental plan  although  it  may  be  modified  into  almost  every  conceiv- 
able variety  to  serve  a  great  diversity  of  functions.  The  hand  of 
man,  the  paddle  of  the  whale,  the  wing  of  the  bat,  etc.,  are  funda- 
mentally the  same.  Comparisons  of  higher  invertebrate  (articu- 
lated) types  show  a  common  plan  of  organization.  Beginning  with 
the  simplest  animals,  a  progressive  series  may  be  roughly  construct- 
ed as  follows:  protozoa,  lower  invertebrates  (double-walled  sac 
t}rpe),  higher  invertebrates  (double-tube  type),  vertebrates. 

4.  The  Distribution  of  Animals. — Not  only  distribution 
throughout  the  various  geographical  provinces  of  the  earth,  but 
also  vertical  distribution  (mountain-top,  valley,  depth  of  the  sea, 
etc.,)  is  included.  Present  distribution  intelligible  only  upon  the 
theory  that  through  migration  from  one  parental  source  to  new 
conditions  and  through  subsequent  multiplication  and  modifica- 
tions, the  kindred  species,  genera,  etc.,  which  occupy  the  same  or 
adjoining  areas,  have  arisen.  Great  importance  of  barriers.  Pecu- 
liarities of  the  fauna  of  oceanic  islands  can  be  explained  only  upon 
the  principles  of  distribution;  absence  of  amphibia  and  terrestrial 

w 


mammals,  presence  of  flying  mammals  and  birds.  Eelation  of  is- 
land forms  to  the  nearest  mainland. 

5.  Some  Recent  Problems  in  Distribution:  Base  Levelling. — 

Tendency  of  elevated  level  tracts  to  be  reduced  to  a  base  level  by 
the  action  of  rivers  and  streams.  Thus  cliffs  and  valleys  are 
formed  and  the  animal  and  plant  inhabitants  must  meet  the  very 
different  new  conditions.  Divides  may  finally  be  surmounted  and 
the  fauna  of  the  two  sides  mingle.  The  separation  of  river  sys- 
tems has  played  an  important  part  in  the  distribution  of  many  ani- 
mals, for  example,  the  snails  of  the  South-eastern  United  States. 

6.  Conclusions.— The  natural  system  of  classification,  the 
structural  affinities  of  living  organisms  and  their  present  distribu- 
tion, all  point  to  community  of  descent. 

LECTUKE  V. 

EVOLUTION;  HISTORICAL  EVIDENCE. 

1.  Nature  of  the  Evidence.— Historical  evidence  conveniently 
classified  into  (a)  history  of  the  race  (geological  record)  and  (b) 
history  of  the  individual.  The  living  forms  about  us  today  are 
but  the  temporary  expressions  of  a  flow  of  life  which  began  in  the 
remote  past.  The  paleontologist  finds  evidence  of  this  in  the 
rocks  and  the  embryologist  sees  it  indelibly  stamped  on  each  new 
organism  that  appears. 

2.  The  Testimony  of  Ancestors.— Fossils  are  the  preserved 
remains  of  the  former  inhabitants  of  the  earth  and  consist  for  the 
most  part  of  hard  substances  preserved  in  nearly  their  original 
state,  or  of  less  permanent  parts  which  have  been  replaced  by  min- 
eral matter.  They  are  found  in.  the  various  strata  which  make  up 
the  crust  of  the  earth.  There  is  a  general  advance  in  the  organiza- 
tion of  fossils  from  lower  to  higher  strata.  Eecent  fossils  are 
closely  allied  to  the  modern  plants  and  animals,  likewise  the  forms 
found  in  successive  geological  periods  are  very  evidently  related. 
Moreover,  as  they  occur  deeper  in  the  series  of  rocks,  they  converge 
more  and  more  toward  a  common  ancestry.  Imperfection  in  the 
geological  record : 

(a)  Our  knowledge  is  more  imperfect  than  the  actual  record 
(material,  inaccessible  or  unexplored). 

(b)  The  chances  against  preservation  are  many.  But  few 
forms  die  in  suitable  localities.  Most  soft  animals  leave  no  trace. 
Many  others  are  devoured  or  dissolved. 

(c)  To  preserve  a  series  of  forms  the  deposits  must  extend 
over  a  very  long  time. 

(d)  It  is  extremely  hard  to  distinguish  between  lineal  de- 
scendants and  collateral  kinsmen  (parents  from  uncles  and  aunts). 

(e)  The  shifting  of  the  various  strata  may  lead  to  misinter- 
pretation. 

(9) 


In  general  the  geological  succession  of  animals  from  the  sim- 
plest to  mammals  may  be  indicated  as  follows :  Single-celled  ani- 
mals (protozoa),  lower  invertebrates,  higher  invertebrates,  fishes, 
reptiles,  mammals. 

3.  The  Life  History  of  the  individual.— The  tadpole  of  the 
common  frog,  is  practically  a  fish  (two-chambered  heart,  gills, 
etc. ) ,  hence  the  frog  repeats  a  fish  stage  in  the  conrse  of  its  devel- 
opment. Higher  vertebrates  go  through  both  a  fish  and  a  frog 
stage  (gill-clefts  and  two-chambered  heart  followed  by  lungs  and. 
three-chambered  heart,  etc.).  All  vertebrates,  moreover,  in  the 
course  of  their  development  pass  through  the  following  well- 
marked  primitive  stages  beginning  with  the  simplest  type  of  or- 
ganism :  A  single  cell,  a  ball  of  cells*  a  double-walled  sac,  a  double 
tube  and  lastly  the  successive  vertebrate  stages,  if  the  form  is  of  the 
highest  type  of  vertebrate.  This  sequence  is  also  the  same  as  that 
seen  in  the  grades  of  structure  observed  among  living  animals  and 
in  the  successive  appearance  of  animals  in  the  history  of  the  earth. 
In  other  words,  the  developing  individual  passes  through  its  succes- 
sive ancestral  stages.  The  presence  of  rudimentary  or  vestigeal 
organs  which  are  useless  to  the  possessor  are  explained  by  this 
tendency  of  living  forms  to  repeat  ancestral  characters.  Falsifica- 
tion of  the  ancestral  history  may  occur  through  condensation, 
omission  or  distortion  of  ancestral  stages. 

4.  Summary  of  Conclusions  From  the  Structure  and  From  the  Ra- 
cial and  Individual  History  of  Animals. 


Single 

Cell. 

Double- 
walled 
Sac. 

Double- 
tube 
Type. 

VERTEBRATE 

Funda- 
mental 
Sturcture 

Two- 
chamber- 
ed heart, 
gillclefts 

Three- 
chamber- 
ed Heart. 
Lungs. 

Four- 
chamber- 
ed Heart, 
lungs. 

Gradation 

of 
structure  in 
living  ani- 
mals. 

(Classifica- 
tion) 

Order  of  ap- 
pearance of 
animals  in 
the   history 
of  the  earth 
(Geology.) 

Stages  in 
the  develop- 
ment of  a 
mammal. 

Protozoa 

Protozoa 
Egg 

Lower  In- 
vertebrate 

Lower  In- 
vertebrate 
(structure?) 

Lower  In- 
vertebrate 

Higher  In- 
vertebrate 

Higher  In- 
vertebrate 

Higher  In- 
vertebrate 

Fish 

Fish 
Fish 

Reptile 

Reptile 
Reptile 

Mammal 

Mammal 
Mammal 

(10) 


LECTUEE  VI. 
THE  DESCENT  OF  MAN. 

1.  The  Zoological  Position  of  Man.— Man  is  distinctly  an 
animal,  a  vertebrate  and  a  mammal  in  structure  and  functions. 
Arguments  concerning  the  origin  of  man  are  of  the  same  general 
nature  as  those  used  to  substantiate  the  descent  of  other  animals. 
Structurally,  man  differs  less  from  the  higher  apes  than  do  they 
from  the  lower.  His  body  a  veritable  memorandum  of  his  past  ex- 
istence; about  seventy  rudimentary  organs  are  homologous  to  kind- 
red organs  which  are  functional  in  lower  animals.  In  his  individ- 
ual development,  man  like  other  mammals  starts  as  a  single  cell 
and  ascends  the  entire  scale  of  transformation  (fish  stage,  reptilian 
stage,  etc.).  The  evidence  from  fossil  remains  of  prehistoric  man 
is  incomplete  but  recent  discoveries  tend  to  confirm  the  fact  that 
man  is  the  outcome  of  natural  evolution. 

2.  Some  Possible  Factors  in  the  Evolution  of  Man: — 

(c)  Dependence  upon  cunning  rather  than  upon  strength 
would  quicken  intelligence. 

(o)  Use  of  tools  and  weapons  and  development  of  instincts 
to  build  shelter. 

(c)  Prolo?iged  infancy  would  call  forth  parental  solicitude. 

(d)  Social  life. 

(e)  Language. 

3.  Evolution  of  Mind.  —All  living  organisms  possess  the 
power  of  response  to  external  stimuli.  Stimuli  are  for  the  produc- 
tion of  activity  and  the  degree  of  the  response  depends  upon  the 
nature  of  the  responding  mechanism.  Such  activities  as  are  for 
the  good  of  the  organism  preserve  it,  those  which  are  harmful  lead 
to  its  destruction.  Variation  in  the  nature  of  responses  occur  and 
this  makes  specialization  possible  through  the  accumulation  of 
serviceable  variations  in  one  direction.  The  mechanism  for  re- 
sponse must  always  be  efficient  for  the  work  that  is  to  be  per- 
formed. In  plants  and  the  simplest  animals  the  mechanism  is 
largely  unspecialized  and  the  responses,  though  adequate,  are  very 
limited  in  range.  In  the  higher  animals,  through  the  physiological 
division  of  labor,  a  number  of  special  elements  are  set  apart  for  the 
perception  of  different  external  stimuli  (sound,  light,  odor,  etc.), 
and  in  degree  as  each  aids  in  the  preservation  of  the  possessor  it 
will  become  more  effective,  because  the  organism  it  has  preserved 
will  live  and  hand  it  down  as  an  heirloom  to  the  succeeding  genera- 
tion to  be  again  the  conserver  of  those  individuals  which  possess  it 
in  the  greatest  degree.  Experience  is  attained  through  the  ac- 
tivity of  our  senses.  We  know  only  through  our  experience  or  the 
experience  of  others  expressed  in  terms  of  our  own  experience. 

(11) 


Thus  all  knowledge,  all  interpretation  of  phenomena  about  us, 
must  be  based  on  experience.  Science  itself  is  but  the  experiences 
of  man  arrangd  in  orderly  form. 

4*  Ethical  Aspect  of  Darwinism.— The  struggle  for  existence 
does  not  cease  with  the  introduction  of  social  institutions.  Co-op- 
eration is  a  powerful  aid  to  the  safety  of  the  participants.  The  ex- 
istence of  an  organism  is  conditioned  by  its  reactions  to  the  reali- 
ties of  the  external  world.  The  accuracy  with  which  it  determines 
these  realities  depends  upon  the  degree  of  perfection  of  its  sensa- 
tions. The  sane  man,  the  man  with  normal  responses  to  the  objec- 
tive world,  will  in  the  end  survive.  That  he  has  survived  is  proof 
that  his  ancestors  have  found  safety  through  the  action  of  their 
sensory  mechanism.  All  defects  in  nervous  responses  lead  to  ac- 
tion based  on  false  perception  and  consequently  hazard  life.  In- 
sanity means  death.  Not  sentiment  but  sanity  must  deal  with 
social  problems.  The  importance  of  conventionality  in  society 
means  that  it  is  a  tried  course  along  which  safety  has  been  found ; 
herein  lies  one  value  of  the  authority  of  the  church  for  the  masses. 
Fear  of  the  unknown  and  worship  of  invisible  powers  has  re- 
strained the  instinctive  tendencies  of  man  and  aided  in  rational 
self-control.  Unrestrained  impulse  means  destruction.  A  living 
organism,  as  already  noted,  is  constructed  to  respond  to  its  environ- 
ment; for  example,  light  renders  the  development  of  eyes  possible; 
there  is  air  to  breathe  and  there  are  organs  for  breathing  it ;  a  fish 
must  have  gills,  and  an  animal  lungs,  for  obtaining  it.  So,  too,  the 
mental  part  of  an  organism  is  conditioned  by  its  environment  and 
a  man  developed  under  one  set  of  conditions  cannot  be  expected  to 
possess  the  same  mechanism  and  show  the  same  responses  as  his 
neighbor  whose  training  and  general  condition  of  life  have  been 
very  different.  Both  will  arrive  at  part  of  the  truth  and  neither 
at  all  of  it.  The  imaginary  conflict  of  science  and  religion,  or  the 
differences  between  monism  and  dualism  are  doubtless  due  to  this 
fact.  Various  men  may  see  the  same  truth  but  proclaim  it  "each 
in  his  own  tongue." 

"A  fire-mist  and  a  planet — 

A  crystal  and  a  cell,— 

A  jelly-fish  and  a  saurian, 

And  caves  where  the  cave-men  dwell; 

Then  a  sense  of  law  and  beauty, 

And  a  face  turned  from  the  clod, 

Some  call  it  Evolution, 

And  others  call  it  God." 


(12) 


UNIVERSITY  OF  ILLINOIS-URBANA 


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